Connecting two units

[john37]

Can someone please review this and let me know if it makes sense? I am installing two mammogram units in two seperate rooms. I'll be taking power off an existing 480/120V, 3 phase panel and adding a new 30KVA transformer with a new 208/120V, 3 phase panel. Cut sheet calls for a 208V, single phase 35A breaker.

 

[iwire]

You need some over current protection between the transformer and the 100 amp panel.

 

[david luchini]

Can someone please review this and let me know if it makes sense? I am installing two mammogram units in two seperate rooms. I'll be taking power off an existing 480/120V, 3 phase panel and adding a new 30KVA transformer with a new 208/120V, 3 phase panel. Cut sheet calls for a 208V, single phase 35A breaker.

You need a OCPD either within or before the panelboard per (408.36.)

I see Bob types faster than I do.

 

[charlie b]

I do not understand the layout. I see two identical setups. In each one, a single pole, 20 amp circuit performs an EPO function. Both setups have a pair of two-pole, 35 amp breakers, one at the panel and one (I infer) near the equipment. Each EPO will shunt trip both its associated 35 amp breakers. That part makes sense.

What I don't get is the relationship between the two 35 amp breakers in each setup. Are they in series? Is the one near the equipment serving a "local disconnect" function? If so, then why is the breaker in the panel connected to the power conditioner, and not to the local breaker? In other words, looking only at the drawing, I do not see how current flows from the panel and through the local breaker.

 

[john37]

Thanks. I see your point. Please see revised one line and let me know if I'm showing it correctly now.

 

[charlie b]

Better. But I suggest one more change. This is a one-line diagram. You show three phase runs, and single pole runs, and two pole runs, each with a single line. But the two pole breakers on the right (near the equipment) have two lines going from them to the power conditioners. It looks like power on one side of the breaker comes in from the panel and leaves without being switched. I think you should show only one line from the enclosed breaker to the power conditioner (i.e., remove the left hand line).

 

[john37]

Great. Thanks Charlie. Yes, you are correct. I'll remove one of the lines.
Appreciate your help!